Re: [PATCH] remap_file_pages: kernel-doc corrections

Re: [PATCH] remap_file_pages: kernel-doc corrections

[Nick Piggin]

On Tuesday 09 October 2007 10:03, Randy Dunlap wrote:
> From: Randy Dunlap <randy.dunlap@oracle.com>
>
> Fix kernel-doc for sys_remap_file_pages() and add info to the __prot NOTE.

Why not just get rid of the double underscore, I wonder?

Pity that prot always has to be PROT_NONE on most architectures (rather
than the current vma's prot)... but that's something which had to have been
picked up years ago.

>
> Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
> ---
>  mm/fremap.c |   20 +++++++++++---------
>  1 file changed, 11 insertions(+), 9 deletions(-)
>
> --- linux-2.6.23-rc9-git3.orig/mm/fremap.c
> +++ linux-2.6.23-rc9-git3/mm/fremap.c
> @@ -97,23 +97,25 @@ static int populate_range(struct mm_stru
>
>  }
>
> -/***
> - * sys_remap_file_pages - remap arbitrary pages of a shared backing store
> - *                        file within an existing vma.
> +/**
> + * sys_remap_file_pages - remap arbitrary pages of a shared backing store

I think the "vma" part is kind of important, and probably not emphasised
enough in the original, and "shared backing store file" is a bit vague. It's
actually a VM_SHARED _vma_.

(which is a bit funny eg. it must be a PROT_WRITE && MAP_SHARED vma
-- doesn't seem to be documented in the man page, and odd that you aren't
allowed to have readonly nonlinear mappings, but it's not mine to wonder
why).

Otherwise, looks OK.

> file * @start: start of the remapped virtual memory range
>   * @size: size of the remapped virtual memory range
> - * @prot: new protection bits of the range
> - * @pgoff: to be mapped page of the backing store file
> + * @__prot: new protection bits of the range (see NOTE)
> + * @pgoff: to-be-mapped page of the backing store file
>   * @flags: 0 or MAP_NONBLOCKED - the later will cause no IO.
>   *
> - * this syscall works purely via pagetables, so it's the most efficient
> + * sys_remap_file_pages remaps arbitrary pages of a shared backing store
> file + * within an existing vma.
> + *
> + * This syscall works purely via pagetables, so it's the most efficient
>   * way to map the same (large) file into a given virtual window. Unlike
>   * mmap()/mremap() it does not create any new vmas. The new mappings are
>   * also safe across swapout.
>   *
> - * NOTE: the 'prot' parameter right now is ignored, and the vma's default
> - * protection is used. Arbitrary protections might be implemented in the
> - * future.
> + * NOTE: the '__prot' parameter right now is ignored (but must be zero),
> + * and the vma's default protection is used. Arbitrary protections
> + * might be implemented in the future.
>   */
>  asmlinkage long sys_remap_file_pages(unsigned long start, unsigned long
> size, unsigned long __prot, unsigned long pgoff, unsigned long flags)

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Re: [PATCH v2] remap_file_pages: kernel-doc corrections

[Nick Piggin]

On Tuesday 09 October 2007 14:29, Randy Dunlap wrote:

> I modified that comment based on your comments.
> See if it's better now, please.

Thanks, looks good.

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[PATCH] remap_file_pages: kernel-doc corrections

[Randy Dunlap, Randy Dunlap]

Fix kernel-doc for sys_remap_file_pages() and add info to the __prot NOTE.

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
---
 mm/fremap.c |   20 +++++++++++---------
 1 file changed, 11 insertions(+), 9 deletions(-)

--- linux-2.6.23-rc9-git3.orig/mm/fremap.c
+++ linux-2.6.23-rc9-git3/mm/fremap.c
@@ -97,23 +97,25 @@ static int populate_range(struct mm_stru
 
 }
 
-/***
- * sys_remap_file_pages - remap arbitrary pages of a shared backing store
- *                        file within an existing vma.
+/**
+ * sys_remap_file_pages - remap arbitrary pages of a shared backing store file
  * @start: start of the remapped virtual memory range
  * @size: size of the remapped virtual memory range
- * @prot: new protection bits of the range
- * @pgoff: to be mapped page of the backing store file
+ * @__prot: new protection bits of the range (see NOTE)
+ * @pgoff: to-be-mapped page of the backing store file
  * @flags: 0 or MAP_NONBLOCKED - the later will cause no IO.
  *
- * this syscall works purely via pagetables, so it's the most efficient
+ * sys_remap_file_pages remaps arbitrary pages of a shared backing store file
+ * within an existing vma.
+ *
+ * This syscall works purely via pagetables, so it's the most efficient
  * way to map the same (large) file into a given virtual window. Unlike
  * mmap()/mremap() it does not create any new vmas. The new mappings are
  * also safe across swapout.
  *
- * NOTE: the 'prot' parameter right now is ignored, and the vma's default
- * protection is used. Arbitrary protections might be implemented in the
- * future.
+ * NOTE: the '__prot' parameter right now is ignored (but must be zero),
+ * and the vma's default protection is used. Arbitrary protections
+ * might be implemented in the future.
  */
 asmlinkage long sys_remap_file_pages(unsigned long start, unsigned long size,
 	unsigned long __prot, unsigned long pgoff, unsigned long flags)

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[PATCH v2] remap_file_pages: kernel-doc corrections

[Randy Dunlap]

On Mon, 8 Oct 2007 18:44:42 +1000 Nick Piggin wrote:

> > Fix kernel-doc for sys_remap_file_pages() and add info to the __prot NOTE.
> 
> Why not just get rid of the double underscore, I wonder?

ok, did that.

> > -/***
> > - * sys_remap_file_pages - remap arbitrary pages of a shared backing store
> > - *                        file within an existing vma.
> > +/**
> > + * sys_remap_file_pages - remap arbitrary pages of a shared backing store
> 
> I think the "vma" part is kind of important, and probably not emphasised
> enough in the original, and "shared backing store file" is a bit vague. It's
> actually a VM_SHARED _vma_.

I modified that comment based on your comments.
See if it's better now, please.

---

From: Randy Dunlap <randy.dunlap@oracle.com>

Fix kernel-doc for sys_remap_file_pages() and add info to the 'prot' NOTE.
Rename __prot parameter to prot.

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
---
 mm/fremap.c |   24 +++++++++++++-----------
 1 file changed, 13 insertions(+), 11 deletions(-)

--- linux-2.6.23-rc9-git3.orig/mm/fremap.c
+++ linux-2.6.23-rc9-git3/mm/fremap.c
@@ -97,26 +97,28 @@ static int populate_range(struct mm_stru
 
 }
 
-/***
- * sys_remap_file_pages - remap arbitrary pages of a shared backing store
- *                        file within an existing vma.
+/**
+ * sys_remap_file_pages - remap arbitrary pages of an existing VM_SHARED vma
  * @start: start of the remapped virtual memory range
  * @size: size of the remapped virtual memory range
- * @prot: new protection bits of the range
- * @pgoff: to be mapped page of the backing store file
+ * @prot: new protection bits of the range (see NOTE)
+ * @pgoff: to-be-mapped page of the backing store file
  * @flags: 0 or MAP_NONBLOCKED - the later will cause no IO.
  *
- * this syscall works purely via pagetables, so it's the most efficient
+ * sys_remap_file_pages remaps arbitrary pages of an existing VM_SHARED vma
+ * (shared backing store file).
+ *
+ * This syscall works purely via pagetables, so it's the most efficient
  * way to map the same (large) file into a given virtual window. Unlike
  * mmap()/mremap() it does not create any new vmas. The new mappings are
  * also safe across swapout.
  *
- * NOTE: the 'prot' parameter right now is ignored, and the vma's default
- * protection is used. Arbitrary protections might be implemented in the
- * future.
+ * NOTE: the 'prot' parameter right now is ignored (but must be zero),
+ * and the vma's default protection is used. Arbitrary protections
+ * might be implemented in the future.
  */
 asmlinkage long sys_remap_file_pages(unsigned long start, unsigned long size,
-	unsigned long __prot, unsigned long pgoff, unsigned long flags)
+	unsigned long prot, unsigned long pgoff, unsigned long flags)
 {
 	struct mm_struct *mm = current->mm;
 	struct address_space *mapping;
@@ -125,7 +127,7 @@ asmlinkage long sys_remap_file_pages(uns
 	int err = -EINVAL;
 	int has_write_lock = 0;
 
-	if (__prot)
+	if (prot)
 		return err;
 	/*
 	 * Sanitize the syscall parameters:

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